1. Field of the Invention
This invention relates to a method for controlling the rotational frequency of a weaving machine and an apparatus therefor and, more particularly, to a method for controlling the rotational frequency of a weaving machine so as to increase the quantity of production and an apparatus therefor.
2. Description of the Prior Art
In a weaving machine, the rotational frequency to maximize the quantity of production depends upon not only the kind of the weaving machine and resultant woven fabric, but also upon the skill of an operator and the tolerance limit of the quality of woven fabric or the like. Thus, in the weaving machine, there is the case where the quantity of production is reduced by increasing the rotational frequency while there is another case where the quantity of production is increased by reducing the rotational frequency.
The above cases take place for the reason that since end breakage of warp and unsatisfactory weft insertion are liable to occur by increasing the rotational frequency, the number of times of stop, or the stop frequency, of the weaving machine caused by the end breakage of warp and unsatisfactory weft insertion is increased. When the stop frequency of the weaving machine is increased, the working allowance of the operator and the operating rate of the weaving machine are reduced thus resulting in the further reduction in quantity of production, and besides, the degradation in quality of woven fabric occurs.
As one of weaving machine control methods which permit the quantity of production to increase by controlling the rotational frequency of a weaving machine, Japanese Patent Public Disclosure (KOKAI) No. 61-239057 (U.S. Pat. No. 4,736,324, EP-A-0182382) has disclosed a method of increasing the rotational frequency of a weaving machine when an allowance is made for the operating rate of the weaving machine.
According to this conventional control method, however, since the rotational frequency is increased only when the operating rate is less than the upper limit thereof, it is unobvious how much the allowance to be made for the operating rate, and in consequence, how much the rotational frequency should be increased. Thus, in the conventional control method, if a variation value of the rotational frequency is defined as an extensive value, the control becomes unstable, so that the rotational frequency should be increased by small degrees, and a lot of time is required before the quantity of production is actually increased.